As well known, the threads used to weave industrial fabrics or footwear fabrics are generally polyester, nylon, acrylic resins, or the like.
The fabrics made of these threads are not only poor in durability and wear resistance but also problematic in the adhesive properties and thus have many limitations on their functional use such as for footwear fabrics or the like.
In addition, the development of softer fabrics has been on consistent demand in order to improve the tactility of fabrics in human body regions, so many attempts have been made to solve the problem by using thermoplastic polyurethane resins.
In the fabrication of threads using thermoplastic polyurethane, however, the spinning methods such as for manufacturing polyester or nylon threads have a high processing cost and the inherent characteristics of thermoplastic polyurethane such as viscosity, tackiness, etc. bring about many difficulties in the manufacture of thermoplastic polyurethane threads.
A conventional solution to this problem involves coating the surface of polyester, nylon or acrylic threads with PVC or PP or manufacturing a thermoplastic polyurethane thread of at least 1,000 denier as shown in the cited patent document 3.
However, the coated threads (more specifically, coated polyester, nylon or acrylic threads) are poor not only in the durability and wear resistance but also in the properties including mechanical/chemical strengths, etc.
Further, all the cited patent documents 1, 2 and 3 have a problem that the threads have high stiffness due to the thread fineness of 1,000 denier or greater and thus are not suitable for use in footwear fabrics.
In addition, the cited patent document 5 involves low viscosity in the use of thermoplastic polyurethane, which eventually deteriorates the productivity, makes it impossible to make thin coated threads and creates the glossy surface of coated threads, thereby causing a demand for a separate process for providing a flattening (deglossing) effect.